An Analysis of Base Station Location Accuracy within Mobile
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Liam Smit, Adrie Stander and Jacques Ophoff Department of Information Systems University of Cape Town South Africa [email protected], {adrie.stander, jacques.ophoff}@uct.ac.za Abstract—An important feature within a mobile-cellular net- work is that the location of a cellphone can be determined. As long as the cellphone is powered on, the location of the cellphone can always be traced to at least the cell from which it is receiving, or last received, signal from the cellular network. Such network-based methods of estimating the location of a cellphone is useful in cases where the cellphone user is unable or unwilling to reveal his or her location, and have practical value in digital forensic investigations. This study investigates the accuracy of using mobile-cellular network base station information for estimating the location of cellphones. Through quantitative analysis of mobile-cellular network base station data, large variations between the best and worst accuracy of recorded location information is exposed. Thus, depending on the requirements, base station locations may or may not be accurate enough for a particular application. Index Terms—Mobile-cellular network, Base station, Cell- phone, Location, Information accuracy I. I NTRODUCTION It is well known that the location of a cellphone, and thus the location of its user, can be determined with a certain degree of accuracy. This information can be used to offer various location-based services and creates the opportunity to build new information services that can be useful to both cellphone users and companies. In addition, location information can be used in other scenarios, such as providing law enforcement agencies with tracking data [1]. One example is that of a murder suspect being found by police after inserting his SIM card into the cellphone of a murder victim [2]. Location information can be used to aid police in tracking movements during investigations and locating suspects. How- ever, it can also be valuable in tracing people for humanitarian reasons, such as search-and-rescue teams defining search areas for locating missing persons. By increasing the accuracy of location information the process of finding the cellphone and its user can be made faster, simpler, and cheaper. In borderline cases it can be the difference between finding someone in need of medical attention in time, or catching a suspect who would have otherwise escaped. Many of the most feasible methods for estimating the loca- tion of a cellphone within a mobile-cellular network depends on using the location of network base stations as known refer- ence points from which to calculate the estimated position of the cellphone. The benefit of such network-based approaches is that no modifications to the handset or network are required. However, by using network, handset, or hybrid approaches the accuracy of location information can be improved [1]. This study investigates the accuracy with which the lo- cations of network base stations are known, as inaccuracy can impair the ability of many of the most feasible methods to provide accurate cellphone location estimates. It starts by providing background information on current techniques for determining the location of a cellphone within a mobile- cellular network. Thereafter the research methodology fol- lowed in the investigation is discussed, followed by a report of the data collected. Finally, the findings are presented and the implications are highlighted. II. BACKGROUND Many handset and network techniques for determining location exist. The most widely known, using the internal hardware of the cellphone, is satellite positioning using GPS but WiFi, Bluetooth, and augmented sensor networks can also be employed [3], [4], [5]. The accuracy of these techniques can vary depending on the technology, line-of-sight, and sensor network coverage [6]. An improvement is to use such hardware in combination with mobile-cellular network information, such as in the case of Assisted-GPS (A-GPS) which uses network resources in the case of poor signal reception. In addition new algorithms have greatly improved the ac- curacy and efficiency with which a cellphone can calculate its position [7], [8]. However, major obstacles including high energy usage and non-availability of features in older cell- phones remain. Thus using location methods based primarily on mobile-cellular network information is widespread. Global System for Mobile Communications (GSM) net- works were not originally designed to calculate locations for the cellphones which access and make use of the network. Many methods have been proposed and developed to be retro- fitted to existing networks [9]. There are a range of accuracies and costs associated with the various methods. The following are the most feasible methods, in order of increasing potential accuracy. • Cell identification (Cell ID) is the simplest location esti- mation method available, but also the least accurate. The estimated area is at best a wedge shaped area, comprising roughly a third of the cell (for three sectored sites), but An Analysis of Base Station Location Accuracy within Mobile-Cellular Networks International Journal of Cyber-Security and Digital Forensics (IJCSDF) 1(4): 272-279 The Society of Digital Information and Wireless Communications (SDIWC) Dec. 2012 (ISSN: 2305-0012) 272
An Analysis of Base Station Location Accuracy within Mobile
